1. Field of the Invention
This invention pertains generally to trenching machines. Specifically, this invention pertains to an improvement to such a machine, whereby boulders which are excavated intact are crushed prior to being deposited onto the refuse conveyor belt.
2. Prior Art
The device with which the present invention will find primary utility is the large trenching machine. These machines are used to dig the trenches in the ground into which pipe, power line, cables and other apparatus are laid. Often, these machines are used to dig trenches spanning distances up to hundreds and even thousands of miles, with the resultant trenches being up to 10 ft. or more deep and 6 ft. or more wide. The earthen material to be trenched can range from soft dirt to rock harder than concrete. Regardless of the hardness of the material being trenched, a particular problem is presented by rocks and boulders which are often encountered and dislodged intact by the machine.
When such a large rock or boulder is encountered, one of three things typically happens. If the boulder is so large, so hard and so firmly embedded that the trenching machine cannot break or remove it, the trenching operation slows considerably as the trenching machine digs its way through the large boulder. This slows the operation, but is not a problem otherwise. Or, the boulder may be broken into several small pieces when hit by the trenching machine, in which case the smaller pieces are removed by the machine from the trench in the normal course and the progress of the machine proceeds unimpeded. Lastly, however, and this is often the case, the entire boulder is dislodged intact, and is then excavated from the trench by the machine and transported to the conveyer belt where it is literally dropped onto the conveyer belt along with the surrounding earth and matter.
Several problems may be encountered when this occurs. First, the conveyer belt or its underpinnings may be damaged when the large, heavy boulder is dropped upon it. Second, even if the conveyer belt is not damaged, the boulder may be too large to fit through the "window" in the frame of the trencher through which the dirt is expelled. In that case, the boulder becomes wedged in the window in the frame, requiring that the trenching operation be stopped completely while the rock is removed. Even if the rock or boulder is small enough to exit the trencher, it cannot be used for back filling the trench after the pipe or other apparatus is laid. Accordingly, that boulder either remains at the site or, as is most often the case, must be transported elsewhere.
The trenching machines with which this invention is primarily used have been in existence for several years. These devices typically comprise a large track-laying motorized vehicle, which is used both to move the trencher forward and to provide a power take-off source for the trenching component of the device. Various types of trenching components are known and used. One is a rotating trenching wheel having buckets which cut the trench and excavate the dislodged earthen material from the trench; another is referred to as a "chain-saw" type trenching component, which resembles a large chain-saw blade attached to and powered by the track-laying vehicle. The "chain-saw" portion typically comprises a large elongated boom around the periphery of which travels a digging belt having a combination of digging teeth which simultaneously cut the earthen material to be extracted and then carry it out of the trench into the body of the trenching component, where it is deposited on a transversely-running conveyor belt which moves the dirt and other material extracted to the side of the trench. After the pipe (or other apparatus) is laid in the trench, the extracted dirt is used to refill the trench. This invention is intended for use with this boom-type trenching machine.
None of the existing prior art trenching machines deal effectively with the problems posed by these dislodged boulders. One attempted solution was to make the "window" in the frame larger, but the problems of damage to the conveyor system and of having the boulders at the trench-site remained. Therefore, a need exists in the field of largescale trenching machines for an improved trencher which will overcome these deficiencies of the prior art.